Chapter 17: Phenomena Phenomena: Mass Moles Boiling Freezing - PowerPoint PPT Presentation

Chapter 17: Phenomena Phenomena: Mass Moles Boiling Freezing Exp. Solute of Solute of Solute Point Point Different masses 1 None 0.0 g 0.00 mol 100.0 ˚ C 0.0 ˚C of solute were added to 1 kg of 2 NaCl 50.0 g 0.85 mol 100.9 ˚ C -3.2 ˚ C either H 2 O or 3 NaCl 100.0 g 1.71 mol 101.7 ˚ C -6.4 ˚ C C 6 H 6 . The boiling H 2 O 4 K 2 O 50.0 g 0.53 mol 100.8 ˚ C -3.0 ˚ C and freezing 5 K 2 O 107.0 g 1.14 mol 101.7 ˚ C -6.3 ˚ C points of the 6 C 12 H 22 O 11 1169.0 g 3.42 mol 101.7 ˚ C -6.4 ˚ C solutions were 7 NaHCO 3 71.7 g 0.85 mol 100.9 ˚ C -3.2 ˚ C then measured. Examine the 8 C 6 H 12 O 6 616.1 g 3.42 mol 101.7 ˚ C -6.4 ˚ C data to Mass Moles Boiling Freezing Exp. Solute determine of Solute of Solute Point Point patterns in how 1 None 0.0 g 0.00 mol 80.1 ˚ C 5.5 ˚ C these variables 2 NaCl 50.0 g 0.85 mol 84.4 ˚ C -3.2 ˚ C affect the boiling 3 NaCl 100.0 g 1.71 mol 88.7 ˚ C -12.0 ˚ C and freezing C 6 H 6 4 K 2 O 50.0 g 0.53 mol 84.1 ˚ C -2.7 ˚ C points of the 5 K 2 O 107.0 g 1.14 mol 88.7 ˚ C -11.9 ˚ C solutions. 6 C 12 H 22 O 11 1169.0 g 3.42 mol 88.7 ˚ C -12.0 ˚ C 7 NaHCO 3 71.7 g 0.85 mol 84.4 ˚ C -3.2 ˚ C 8 C 6 H 12 O 6 616.1 g 3.42 mol 88.8 ˚ C -12.0 ˚ C Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions

Chapter 17 Properties of Big Idea: Liquids will mix Solutions together if both liquids are polar or both are nonpolar. The presence of a solute o Types of Solutions changes the physical o Solubility properties of the o Colligative Properties system. For non- o Vapor Pressure volatile solutes the o Boiling and Freezing Point vapor pressure, boiling o Osmotic Pressure point, freezing point, and osmotic pressure are only dependent on the number of ions/particles. 2

Types of Solutions Matter can be broken in to two subcategories: pure substances and mixtures. Pure Substances  Elements: A substance that cannot be separated into simpler components by chemical techniques.  Compounds: A specific combination of elements that can be separated into its elements by chemical techniques but not by physical techniques. Examples: Examples : Water (H 2 O), salt (NaCl), and sucrose (C 12 H 22 O 11 ) Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 3

Types of Solutions Mixtures  Heterogeneous Mixtures: A mixture in which the individual components, although mixed together, lie in distinct regions that can be distinguished with an optical microscope.  Homogeneous Mixture: A mixture in which the individual components are uniformly mixed, even on the molecular scale. Example: Example: Air (nitrogen, oxygen, argon, …) Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 4

Types of Solutions Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 5

Types of Solutions Student Question How many of the following are homogeneous mixtures? Oil and vinegar Salt water Chalk and table salt Kool-Aid Charcoal and sugar a) 1 is homogeneous b) 2 are homogeneous c) 3 are homogeneous d) 4 are homogeneous e) All are homogeneous Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 6

Types of Solutions  Solution: A homogeneous mixture. Solutions are made up of at least two parts  Solvent: The most abundant component of a solution.  Solute: A dissolved substance. State of Solution State of Solvent State of Solute Example Air Gas Gas Gas Natural gas Tequila Liquid Liquid Liquid Antifreeze Liquid Liquid Gas Soda water Sea water Liquid Liquid Solid Sugar water Alloys (Steel or Solid Solid Solid brass) Hydrogen in Solid Solid Gas platinum Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 7

Types of Solutions Student Question The density of a 40.0% by weight aqueous solution of NaOH is 1.432 𝑕 𝑑𝑛3 . What is the molality of NaOH? Helpful Information: 𝑁 𝑂𝑏𝑃𝐼 = 40.00 𝑕 𝑛𝑝𝑚 a) 12.9 m b) 14.3 m c) 16.7 m d) 13.8 m e) None of the above Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 8

Solubility Exothermic Endothermic Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 9

Solubility Student Question Which one of the following substances would be the most soluble in CCl 4 ? a) CH 3 CH 2 OH b) C 10 H 22 c) H 2 O d) NaCl e) NH 3 Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 10

Solubility Cation and H 2 O Anion and H 2 O  Hydration: The reaction of a substance with water. Not ote: e: For molecules, the extent of hydration increases as polarity increases. Not ote: e: For ions, the extent of hydration increases as charge density (charge per volume) increases. In general, the smaller the size, the larger the charge density and the larger the charge, the larger the charge density. Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 11

Solubility  Saturated Solution: A solution that holds the maximum amount of solute.  Unsaturated Solution: A solution that holds less than the maximum amount of solute.  Supersaturated Solution: A solution that holds more than the maximum amount of solute.  If a solutions is supersaturated any small disturbance can cause the solute to recrystallize Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 12

Solubility  The graph shows the saturation level of different solutions at a given temperature. If a solution has a solubility that results in a point above the line, then the solution is considered to be supersaturated. However, if a solution has a solubility that results in a point under the line, then the solution is considered unsaturated. Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 13

Solubility  k  P H gas Not ote: e: Where 𝝍 is the mole fraction of the gas dissolved in solution. Not ote: e: An alternate form of henry’s Law is: P = 𝑙 𝐼 𝑑 where c is the molarity. Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 14

Colligative Properties  Colligative Properties: Physical properties of solutions that depend on the number of solute particles present but not the type of solute particles.  Examples of Colligative Properties:  Vapor Pressure (non volatile solutes)  Freezing Point  Boiling Point  Osmotic Pressure Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 15

Vapor Pressure  Vapor Pressure: The pressure exerted by the vapor of a liquid or solid.  Volatile: Having a high vapor pressure at ordinary temperatures (evaporates easily).  Nonvolatile: Having a low vapor pressure at ordinary temperatures (does not evaporate easily). Nonvolatile Solute  Raoult’s Law  𝑄 𝑡𝑝𝑚𝑣𝑢𝑗𝑝𝑜 = ° 𝜓 𝑡𝑝𝑚𝑤𝑓𝑜𝑢 𝑄 𝑡𝑝𝑚𝑤𝑓𝑜𝑢 Not ote: e: Where 𝝍 is the mole fraction of the solvent 𝑜𝑡𝑝𝑚𝑤𝑓𝑜𝑢 . 𝑜𝑢𝑝𝑢 Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 16

Vapor Pressure Student Question Which of the following aqueous solutions containing nonvolatile solutes should have the highest boiling point? a) 0.02 m C 6 H 12 O 6 b) 0.02 m (NH 4 ) 2 SO 4 c) 0.02 m NaCl d) 0.02 m Ce(NO 3 ) 4 e) All have the same boiling point Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 17

Vapor Pressure Ideal Solution (Obeys Raoult’s Law)  Which substance (A or B) has the higher boiling point? Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 18

Vapor Pressure Student Question What is the vapor pressure of a solution of 50.0 g of CCl 4 and 50.0 g of CHCl 3 at 25 ˚ C. The vapor pressures at 25 ˚ C for pure CCl 4 and CHCl 3 are 98.3 torr and 172.0 torr respectively. Helpful Information: 𝑁 𝐷𝐼𝐷𝑚 3 = 119.37 𝑕 𝑛𝑝𝑚 and 𝑁 𝐷𝐷𝑚 4 = 153.81 𝑕 𝑛𝑝𝑚 a) 131 torr b) 140. torr c) 149 torr d) 126 torr e) None of the Above Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 19

Vapor Pressure Deviations from Raoult’s Law Ideal Δ H=0 Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 20

Boiling and Freezing Points  Freezing Point Depression: The decrease in the freezing point of a solvent caused by the presence of a solute.  Boiling Point Elevation: The increase in the boiling point of a solution caused by the presence of a solute. Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 21

Boiling and Freezing Points Boiling Point Elevation solid liquid gas  The presence of a nonvolatile solute lowers the vapor pressure of the solution, therefore, a higher temperature must be present in order for the vapor pressure of the solution to reach 1 atm (normal boiling point). Cha hapt pter er 17: P Prop oper erti ties es of of Sol olut utions ions 22